Jacket illustrations: Grasshopper and yellow-billed cuckoo, by James Nardi

They drop from branches, blend in with their surroundings, swarm, sting, and poison their predators. For the 900,000 known insect species, about 75 percent of the known animal species on earth, staying alive by any means necessary requires a variety of defenses.

In his new book, Gilbert Waldbauer, a professor emeritus of entomology at the University of Illinois, uses a plethora of studies from scores of researchers to show that whether they walk, swim, or fly, insects are unparalleled in their ability to eat plants and other insects, parasitize mammals and transmit disease (thus helping to keep populations in check), and function as a sanitation corps by recycling and redistributing nutrients from dung and dead plants and animals.

“An ecosystem with too few insects would be in a precarious state of disarray because they—the most numerous animals as both individuals and species in almost all terrestrial ecosystems—have many important, sometimes indispensable duties,” he writes. At times this informative book turns wonderfully gross and lovely, reminding us that there’s an entire universe of largely unnoticed creatures all around us.